Stray Flux

Stray Flux and its Influence on Protection Relays

by Z. Gajic, S. Holst, ABB AB, SA Products, Sweden, D. Bonmann, ABB AG, Transformers,
Germany, and D. Baars, ELEQ bv. Netherlands

Current transformers (CT) normally have excellent performance when applied correctly under conditions for which they were designed. While the common operating conditions affecting CT performance are usually recognized and properly considered, there is one factor, the importance of which is sometimes underestimated or even overlooked entirely. If a CT is applied incorrectly (e.g. without considering the existence of stray fluxes) the secondary CT current can be, under certain circumstances, entirely different from the primary CT current which then can easily cause unwanted operations of sensitive protection relays like, for example, differential protection. More

Power. Flexible. Easergy.
BeijingSifang June 2016